Agave
Agave is a genus of monocots native to the arid regions of the Americas. The genus is primarily known for its succulent and xerophytic species that typically form large rosettes of strong, fleshy leaves.
Many plants in this genus may be considered perennial, because they require several to many years to mature and flower. However, most Agave species are more accurately described as monocarpic rosettes or multiannuals, since each individual rosette flowers only once and then dies; a small number of Agave species are polycarpic.
Along with plants from the closely related genera Yucca, Hesperoyucca, and Hesperaloe, various Agave species are popular ornamental plants in hot, dry climates, as they require very little supplemental water to survive. Most Agave species grow very slowly. Some Agave species are known by the common name "century plant".
Maguey is a Spanish word that refers to all of the large-leafed plants in the Asparagaceae family, including agaves and yuccas. Maguey flowers are eaten in many indigenous culinary traditions of Mesoamerica.
Nomenclature
In other regions, it goes by different names. In China, it is referred to as the compound word Dragon Tongue Orchid. In Japan and Korea, the same symbols are used as they are in Chinese—and thus the name is the same when translated—but the pronunciation is different, resulting in Dragon Tongue Orchid.In Malta, it is referred to as Sabbara; In Maltese, Agave americana is referred to as "Sabbara tal-Amerika", and Agave sisalana is referred to as "Sabbara ta' Sisal".
Description
The succulent leaves of most Agave species have sharp marginal teeth, an extremely sharp terminal spine, and are very fibrous inside. The stout stem is usually extremely short, which may make the plant appear as though it is stemless.Agave rosettes are mostly monocarpic, though some species are polycarpic. During flowering, a tall stem or "mast", which can grow to be high, and Agave salmiana can be significantly taller. The panicle grows apically from the center of the rosette and bears a large number of short, tubular flowers and sometimes vegetatively produced bulbils. After pollination/fertilization and subsequent fruit development, in monocarpic species, the original rosette dies. However, throughout the lifetime of many Agave species, rhizomatous suckers develop above the roots at the base of the rosette. These suckers go on to form new plants after the original rosette desiccates and dies. Not all agaves produce suckers throughout their lifetimes; some species rarely or never produce suckers, while others may only develop suckers after final maturation with inflorescence. Some varieties can live for 60 years before flowering.
File:Agave shawii shawii rosette life cycle.png|thumb|Agave shawii mast before, during, and after flowering, Cabrillo National Monument
Agaves can be confused with cacti, aloes, or stonecrops, but although these plants all share similar morphological adaptations to arid environments, each group belongs to a different plant family and probably experienced convergent evolution. Further, cactus and stonecrop lineages are eudicots, while aloes and agaves are monocots.
Adaptations
The agave root system, consisting of a network of shallow rhizomes, allows the agave to efficiently capture moisture from rain, condensation, and dew. In addition to growing from seeds, most agaves produce 'pups' – young plants from runners. Agave vilmoriniana produces hundreds of pups on its bloom stalk. Agave leaves store the plant's water and are crucial to its continued existence. The coated leaf surface prevents evaporation. The leaves also have sharp, spiked edges. The spikes discourage predators from eating the plant or using it as a source of water and are so tough that ancient peoples used them for sewing needles. The sap is acidic. Some agaves bloom at a height up to so that they are far out of reach to animals that might attack them. Smaller species, such as Agave lechuguilla, have smaller bloom stalks.Taxonomy
The genus name Agave come from the Ancient Greek αγαυή from ἀγαυός agauós meaning "illustrious, noble" having to do with very tall flower spikes found on its many species.The genus Agave was erected by Carl Linnaeus in 1753, initially with four species. The first listed was Agave americana, now the type species. In the Cronquist system and others, Agave was placed in the family Liliaceae, but phylogenetic analyses of DNA sequences later showed it did not belong there. In the APG II system, Agave was placed in the segregated family Agavaceae. When this system was superseded by the APG III system in 2009, the Agavaceae were subsumed into the expanded family Asparagaceae, and Agave was treated as one of 18 genera in the subfamily Agavoideae, a position retained in the APG IV system of 2016. However, Agavaceae had regained its taxonomic status as an independent family by 2020.
Agaves and close relatives have long presented significant taxonomic difficulty. These difficulties could be due to the relatively young evolutionary age of the group, ease of hybridization between species, incomplete lineage sorting, and long generation times. Within a species, morphological variations can be considerable, especially in cultivation; many named species may be variants of original wild-type species that horticulturalists bred to appear unique in cultivation.
With the advent of DNA sequencing, new karyologic and evolutionary phylogenetic studies showed that the genera Manfreda, Polianthes and Prochnyanthes were genetically nested within the traditional circumscription of Agave, rendering the genus paraphyletic. Early in the 21st century, these new phylogenetic results led to a reclassification of to include Manfreda, Polianthes and Prochnyanthes together as Agave subgenus Manfreda.
There was reaction against the changes from those who noted that the large morphological differences between the genera in this new Agave s.l. making them "counter-intuitive from a horticultural point of view". Manfreda morphologically differs from the classic Agave description in being herbaceous and bulbous, while Polianthes are deciduous with narrow leaves and no spines. Mexican taxonomists have continued to adhere to the traditional classifications and have published new species of Polianthes.
Thus, based on a wider consideration of previously established genetic, morphological, and estimated genetic divergence times, Vázquez-García et al. proposed a narrower circumscription of Agave by creating three new genera: Echinoagave, Paleoagave and Paraagave. These new genera have gained some acceptance, and pave the way for a reconsideration of Manfreda, Polianthes and Prochnyanthes.
Commonly grown species
Some commonly grown species include Agave americana, A. angustifolia, A. attenuata, A. murpheyi, A. palmeri, A. parryi, A. parviflora, A. tequilana, A. victoriae-reginae, and A. vilmoriniana.File:Garing boom.jpg|thumb|A row of agaves in bloom in the Karoo region of South Africa: the inflorescences of the plants are clearly visible.
''A. americana''
One of the most familiar species is A. americana, a native of tropical America. Common names include century plant, maguey, or American aloe. The name "century plant" refers to the long time the plant takes to flower. The number of years before flowering occurs depends on the vigor of the individual plant, the richness of the soil, and the climate; during these years, the plant is storing in its fleshy leaves the nourishment required for the effort of flowering.A. americana, century plant, was introduced into southern Europe about the middle of the 16th century and is now naturalized as well as widely cultivated as an ornamental, as it is in the Americas. In the variegated forms, the leaf has a white or yellow marginal or central stripe. As the leaves unfold from the center of the rosette, the impression of the marginal spines is conspicuous on the still erect younger leaves. The plant is reported being hardy to −9.5 to −6.5 °C or Zone 8b 15-20f. Being succulents, they tend to rot if kept too wet. In areas such as America's Pacific Northwest, they might be hardy for cold winter temperatures, but need protection from winter rain. They mature very slowly and die after flowering but are easily propagated by the offsets from the base of the stem.
A. americana occurs in abundance in the Karoo, and arid highland regions of South Africa. Introduced by the British settlers in 1820, the plant was originally cultivated and used as emergency feed for livestock. Today, it is used mainly for the production of syrup and sugar.